Checking the PendingReturned Flag

Note

For optimal reliability and performance, use file system minifilter drivers with Filter Manager support instead of legacy file system filter drivers. To port your legacy driver to a minifilter driver, see Guidelines for Porting Legacy Filter Drivers.

If a completion routine doesn't signal an event, it must check the Irp‑>PendingReturned flag. If this flag is set, the completion routine must mark the IRP pending by calling IoMarkIrpPending.